# FX6 and FX9 R and B Gain values – don’t worry about the odd numbers.

I’ve noticed some users concerned or confused by the R and B gain values that they see in the cameras white balance settings after dialling in a custom white balance and tint, or after taking a white balance from a white card. The R and B gain values indicate the offset that is being applied to the Red and Blue channels relative to the Green channel and in fact they are perfectly normal.

Typically the concern occurs when someone has used a white card to set their white balance and then these seemingly random numbers appear against the Red and Blue gain. But they are not random, they are expected, normal, and not normally something to every worry about.

The FX6 and FX9 are set up such that the indicated Red and Blue gains will only ever both be 0 when the white balance of the camera is at exactly 3200K. At any other white balance there will be an offset to the R and B gain – and that is completely normal. It is these offsets that balance the Red and Blue levels so that the white balance appears correct. At a lower colour temperature you will see a positive blue value and a negative red value. Above 3200K there will be a positive Red value and a negative Blue value.  A positive tint value will make both the Red and Blue more positive and a negative tint value will make both the Red and Blue values more negative.

All of this is perfectly normal and perfectly expected. If you have taken a white balance off a white card and then dial in a preset value you might find that the you can’t get the last  2 digits back to a zero.

For example after white balancing off a card you have 3653K but you then try to dial in 3200K, but the closest you can get is 3193K or 3213K.  This is because the smallest steps the colour temperature changes in is 20K (on the FX6 above 5640K the steps gradually get larger and larger). But this really isn’t something to worry about 3193K or 3213K are both so close to 3200K that either will do and calibration  and temperature differences will mean that the actual variations between different cameras or the camera and a colour meter will be greater than this error anyway. No two cameras will ever be truly identical and differences between lenses will cause add to this normal variation. There is no need to worry about the last 2 digits not being zero’s.

At the end of the day, these tiny differences are not something to worry or be concerned about. But if you do want to return the last digits back to zero you can do this by dialling the white balance all the way down to 2000K.

# Improve the accuracy of manual white balance with the FX6 and FX9.

Have you ever struggled to get a decent white balance from a white or grey card with the Sony FX6, FX9 or in fact many other cameras (this method works equally well for the FS7, FS5, F5 and F55 etc)? Well here is a very simple trick that can really help, especially for those situations where the camera is a long way from the scene and a white card is too small in the frame for an accurate reading.

All you need to do is to cut a square hole in a piece of black card or plastic. Then when you want to take your white balance simply hold the mask in front of the lens so that it masks out the background of the shot leaving just your white card visible. It’s really simple, really easy and it really works!

# Important Firmware Update For The FX9

A few days ago Sony quietly released a new important firmware update for the PXW-FX9. Firmware version 2.10 adds the long awaited 4K 120fps raw function to the FX9 (you do still need the XDCA-FX9) but also importantly includes some change the the daylight white balance settings.

From my before and after testing it appears that a change has been made to the daylight white balance preset settings. For some time it has been apparent that if you used the white balance presets in the daylight range (4000K and higher) that the FX9 has a tendency to accentuate any green in the image. If you white balance of a white card this tendency is not there.

The new preset white balance settings now provide a much more neutral white balance with less green bias. This should also help those that were suffering from green fringing in extreme contrast shots as the reduced green bias will stop the camera from accentuating chromatic aberration as it did before. It won’t eliminate the chromatic aberration, but it won’t be nearly as obvious.

The first image was taken before doing the firmware update using a preset of 5500K. This test was done in a bit of a hurry as it was threatening to rain, but I wanted to use real daylight.

The second image, below, was taken after the firmware update (unfortunately the focus shifted slightly between the two shots, sorry). But you can clearly see that even though the white balance settings are the same and the same 5500K preset used this image is less green.

It is a subtle difference, but if you look at the wood panels you can  see a difference. To help you see the difference here is a wipe between the before and after clips with the saturation boosted to make it more obvious.

As you can see this isn’t an “in your face” difference. But it is still none the less an important improvement as it makes it easier to match the FX9 to the FX6 and FX3 if you are using a preset white balance. I would still recommend white balancing off a white card for all cameras wherever possible as this will still normally provide the best results as it helps neutralise any lens or calibration differences. Whether you are shooting using S-Cinetone as in the examples here or using S-Log3, the new white balance preset provides in my opinion a much better colour response.

HOWEVER it’s important to consider that it will make cameras with version 2.10 and later look different to FX9’s with earlier firmware versions.

The firmware update can be downloaded via the link below. It took around 35 minutes for my FX9 to complete the update. The process is easy but when the camera gets to 80% complete it will appear that the update has stalled. It stays at 80% for around 10-15 minutes with no indication that the update is still continuing. So don’t turn the camera off thinking it’s stuck!!! Be patient and give it time to complete.

https://pro.sony/en_GB/support-resources/pxw-fx9/software/

# Setting The White Balance When Using The Variable ND Filter

It’s no secret that the variable ND fitted to many Sony cameras does introduce a colour shift that changes depending on how much ND you use. But the cameras are setup to add an offset to the WB as you switch the ND in or out and change the amount of ND, so in practice most people are completely unaware of this shift.

If you watch carefully when you engage or disengage the ND you can sometimes see a fraction of a second where the cameras electronic offset that corrects for the shift is applied just as the filter comes in. Then once the filter is in place the colours appear completely normal again.

So when should you white balance from a white card? With or without the ND filter in place?

You can actually white balance either with or without the ND in place. Because the camera knows exactly what offset to apply for any ND value if you change the ND it will compensate automatically and generally the compensation is very accurate. So in most cases it doesn’t really matter whether the ND filter is in place or not.

However, my personal recommendation is where possible to white balance with the camera setup as it will be when you are taking your footage. This should then eliminate any small errors or differences that may creep in if you do change the ND or switch the ND in or out.

But I wouldn’t be too concerned if you do have to do a WB at one ND level and then change the ND for whatever reason. The in camera compensation is extremely good and you would only ever really be able to see any difference if you start doing careful like for like, side by side, split screen direct comparisons. It’s certainly highly unlikely that you or your audience would ever notice any difference in normal real world applications.

You will often see greater colour shifts if you add external ND filters or swap between different lenses, so treat the internal ND as you would any other ND filter and WB with your lens, filters and everything else as it will be when taking the footage. I think one of the truly remarkable things about the variable ND filter is just how consistent the output of the camera is across such a wide range of ND.

# Why is the white balance limited to 3 presets when using S-Log2, S-Log3 or raw?

This seems to be a source of frustration for many people shooting  raw or using S-Log2 or S-Log3 on a Sony camera. When shooting log and raw you should also be using a matching S-Gamut colour gamut if you want to get the best from the camera and this ties you into one of 3 preset white balances.

With a PXW-FS7, PMW-F5 or F55 it is possible to use custom mode to select a different colour space to mix with S-Log2 or S-Log3 and then have a variable white balance. With the Alpha cameras, PXW cameras such as the FS5 you can choose any Gamut you want in the picture profiles, but I don’t recommend this. For a start, if you don’t use one of the S-Gamuts you will be limited to Rec-709 Gamut, so you won’t be recording  the cameras full colour range. Also in custom mode there are some other things like noise reduction that you really don’t want when shooting S-log2/3 (it can cause banding).

So why is the S-Gamut white balance fixed to the 3 presets for daylight, fluorescent and tungsten? The main reason is to ensure you get the cameras full dynamic range in each colour. White balance is a gain function, it adjusts the gain of the red, green and blue channels so that white objects appear white under differing light sources. So if the light source lacks blue light – making the pictures look excessively warm – you add extra gain to the blue channel to compensate.

But the problem with this is that gain affects dynamic range. When shooting log (or raw) the camera needs to operate the sensor at the optimum gain level to squeeze the highest possible dynamic range from the it. Changing the gain in just one colour channel to shift the white balance could result in a reduction of dynamic range in the channel. This could manifest itself as colours in one channel that clip sooner than the others. This can be really hard to deal with in post production and can show up as things like bright clouds with a colour cast that isn’t in the rest of the picture.

Another potential issue is that because of the way silicon sensors work the blue channel is almost always noisier than the red and green. So you want to keep the gain in the blue channel as low as possible to prevent the pictures getting too noisy. This is particularly important when shooting log as you won’t see your end result until after the images have been graded. So manually shifting the gain of the blue channel in camera to correct the white balance could lead to footage that ends up noisier than you would expect.

So – Sony chose to fix the white balance to 3 carefully tuned presets designed to avoid this situation and maximise the dynamic range. After all, when shooting log or raw it is expected that the footage will be graded anyway, so the white balance will normally be adjusted as part of the post production process.

There are some people that advocate adjusting the FS5’s white balance via the picture profile settings, personally I don’t recommend this or feel that it’s necessary. But yes, you can do this, but just keep a very close eye on your highlights and if you can use monitor with RGB parade to make sure you have equal recording levels for your whites without one colour channel clipping ahead of the others. Also apply a LUT in the monitor that is close to your desired output so that you can keep an eye on the noise levels.

In summary – the white balance is preset to ensure you don’t encounter problems later on. You should be able to fully adjust and fine tune your white balance in post production to a far greater degree than is possible in camera anyway, so don’t worry if the WB is a touch off when shooting.

The only exception to this is the new Sony Venice. Venice has enough dynamic range and enough internal processing power to allow you to make a wide range of white balance adjustments in camera. Hopefully we will see some of this flexibility trickle down to the next generations of lower cost Sony digital cinema cameras.